System and method for near field communications antenna for mobile devices

ABSTRACT

A system for an antenna for near field communications (NFC), said antenna comprising a primary loop with a primary current to produce a magnetic field; one or more secondary loops with one or more secondary currents; wherein by adjusting one or more variables associated with said one or more secondary loops, said magnetic field is modified to ensure antenna operation within a defined operating range.

TECHNICAL FIELD

The present disclosure relates to near field communications (NFC)antennas for mobile devices.

SUMMARY

A system for an antenna for near field communications (NFC), saidantenna comprising a primary loop with a primary current to produce amagnetic field; one or more secondary loops with one or more secondarycurrents; wherein by adjusting one or more variables associated withsaid one or more secondary loops, said magnetic field is modified toensure antenna operation within a defined operating range; and said oneor more variables comprise a number of secondary loops, one or moreamplitudes of the one or more secondary currents in the one or moresecondary loops, one or more phase differences between the one or moresecondary currents in the one or more secondary loops and the primarycurrent in the primary loop, one or more shapes of the one or moresecondary loops; one or more dimensions of the one or more secondaryloops, and one or more placements of the one or more secondary loops.

A method for an antenna for near field communications (NFC), saidantenna comprising a primary loop with a primary current to produce amagnetic field; one or more secondary loops with one or more secondarycurrents; wherein said method comprises modifying said magnetic field toensure antenna operation within a defined operating range; saidmodifying comprising adjusting one or more variables associated withsaid one or more secondary loops, wherein said one or more variablescomprise a number of secondary loops, one or more amplitudes of the oneor more secondary currents in the one or more secondary loops, one ormore phase differences between the one or more secondary currents in theone or more secondary loops and the primary current in the primary loop,one or more shapes of the one or more secondary loops; one or moredimensions of the one or more secondary loops, and one or moreplacements of the one or more secondary loops.

The foregoing and additional aspects and embodiments of the presentdisclosure will be apparent to those of ordinary skill in the art inview of the detailed description of various embodiments and/or aspects,which is made with reference to the drawings, a brief description ofwhich is provided next.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other advantages of the disclosure will becomeapparent upon reading the following detailed description and uponreference to the drawings.

FIG. 1 shows a NFC antenna 100 with primary loop 101 and primary current102 and magnetic field 103;

FIG. 2 shows a NFC antenna 100 with magnetic field 103 enhanced byelement 201;

FIG. 3 shows a NFC antenna 100 with secondary loop 211 and secondarycurrent 212 to reduce the magnetic field strength in the centre ofprimary loop 101;

FIG. 4 shows a NFC antenna 100 with secondary loops 211 and 221, runningsecondary currents 212 and 222, to reduce the enhancement caused byelement 201 and balance the magnetic field; and

FIG. 5 shows an adjustment module 501.

While the present disclosure is susceptible to various modifications andalternative forms, specific embodiments or implementations have beenshown by way of example in the drawings and will be described in detailherein. It should be understood, however, that the disclosure is notintended to be limited to the particular forms disclosed. Rather, thedisclosure is to cover all modifications, equivalents, and alternativesfalling within the spirit and scope of an invention as defined by theappended claims.

DETAILED DESCRIPTION

Referring now to the drawings, wherein like reference numbers are usedherein to designate like elements throughout, the various views andembodiments of system and method for near field communications antennafor mobile devices are illustrated and described, and other possibleembodiments are described. The figures are not necessarily drawn toscale, and in some instances the drawings have been exaggerated and/orsimplified in places for illustrative purposes only. One of ordinaryskill in the art will appreciate the many possible applications andvariations based on the following examples of possible embodiments.

Near field communications (NFC) antennas are used in many mobile devicessuch as smartphones, tablets, laptops, and wearable devices. Thesedevices operate via proximity coupling of magnetic fields. Theseinclude, for example, Europay, MasterCard and Visa (EMV) contactlesscommunications, sharing files between electronic devices, reading of“tags”, and gaming. Various regulatory and standardization bodies havepublished performance requirements for the devices which utilize theseNFC antennas.

Typically, many of these performance requirements stipulate that theseantennas operate within a magnetic field strength range comprising aminimum and maximum magnetic field strength, over a specific operatingvolume. A typical design challenge is then to ensure that an NFC antennais able to operate within this range. This is a difficult challenge dueto the following factors. Due to space constraints, the NFC antennas arerestricted to certain shapes and aspect ratios. This makes it difficultto generate specific three-dimensional (3D) operating shapes. Forexample, in some smartphones the NFC antennas are typically planarloops. The magnetic field pattern is modified by materials close to theNFC antenna. For example, a material with high permeability will amplifythe magnetic field strength. Furthermore, certain materials whichobstruct electromagnetic fields will reduce the magnetic field strengthin a certain area.

While the prior art describes beam steering and beam forming solutionsto face such challenges, most of this prior art is typically targeted tofar-field applications rather than near-field design. This means thatmany of these solutions are not applicable to NFC antennas.

Also, many NFC antennas have dimensions which are orders of magnitudesmaller than the operating wavelength. For example, a typical operatingfrequency for an NFC antenna is 13.56 MHz, implying that the wavelengthis around 22 m. However the typical dimensions of a rectangular loopantenna are around 2-3 inches×1-2 inches (around 5-8 cm×2.5-5 cm). Thismeans that the wavelength is orders of magnitude larger than theantenna. It is well known to those of skill in the art that suchantennas have very poor radiation efficiency. This stands in contrast toantennas designed for far field applications which typically have veryhigh radiation efficiency.

Therefore there is a need for a solution to ensure that a proximitycoupling NFC antenna operates within a certain range and produces acertain operating volume. A system and method to provide such a solutionis described below in the remainder of this specification.

In one embodiment, the NFC antenna comprises a primary loop. Referringto FIG. 1, NFC antenna 100 comprises primary loop 101. By sending asinusoidally varying primary current 102 at a specified operatingfrequency through this primary loop, a magnetic field 103 is generatedwithin a specific operating volume as shown in FIG. 1. In oneembodiment, the operating frequency is set to 13.56 MHz. The principlesof operation of such an NFC antenna are well known to those of skill inthe art and thus will not be discussed further here.

Typically, with such structures, problems may arise. For example, themagnetic field strength may be too high in the center of the loop.

Another problem which could potentially arise is when an element with amaterial that either enhances or suppresses the magnetic field is placedclose to the primary loop. An example is shown in FIG. 2, where element201 which enhances the magnetic field is placed close to the primaryloop. This has the effect of imbalancing magnetic field 103. Then, thestrength of magnetic field 103 is not within the operating range in theoperating volume, or the operating volume is modified. That is, eitherthe magnetic field strength is too high or too low, or the operatingvolume becomes anti-symmetric leading to inconsistent performance of thesystem.

A further problem which could potentially arise is difficulty in meetingthe shape requirement of the specific operating volume using only aprimary loop. For example, it is not easy to realize a cylindricaloperating volume using a rectangular primary loop.

These problems as outlined above, can be overcome by using one or moresecondary loops with one or more sinusoidally varying secondary currentsin the antenna. These secondary currents will have the same operatingfrequency as the primary current in the primary loop. By adjusting oneor more variables such as: the number of secondary loops; the amplitudeof the one or more secondary currents in the one or more secondaryloops; the phase difference between the one or more secondary currentsin the one or more secondary loops and the primary current in theprimary loop; the shape of the one or more secondary loops; thedimensions of the one or more secondary loops; and the placement(s) ofthe one or more secondary loops. It is then possible to modify themagnetic field, to ensure that the antenna operates within the definedoperating range within an operating volume.

For example, with reference to the problem of excessively high magneticfield strength in the center, by placing a secondary loop with asecondary current that is out of phase with the primary current in theprimary loop, as shown in FIG. 3, it is possible to reduce the magneticfield strength in the center such that the antenna operates within theoperating range. While only one secondary loop is shown in FIG. 3, itwould be known to one of skill in the art that one or more secondaryloops could be used.

The settings for the variables mentioned above can be obtained using avariety of techniques. In one embodiment, the settings for the variablesare obtained using numerical simulation. In another embodiment, thesettings for the variables are obtained using analytical techniques andapproximations known to those of skill in the art. In a furtherembodiment, the settings for the variables are obtained via testing andcontinuous adjustment. In other embodiments, said settings are obtainedusing a combination of said techniques.

Similarly, the problem shown in FIG. 2 can be addressed by using one ormore secondary loops close to the material which enhances or suppressesthe magnetic field, as is shown in FIG. 4. In FIG. 4, secondary loop 211carrying secondary current 212 is placed so as to suppress the increasedmagnetic field due to element 201. As explained previously, variablessuch as amplitude and phase difference of the one or more secondarycurrents, and aspect ratio and placement of the one or more secondaryloops, are adjusted so as to obtain the required field strength. In afurther embodiment, so as to improve the symmetry of the fielddistribution throughout the operating volume, one or more secondaryloops are placed away from the material such as secondary loop 221carrying secondary current 222. Then, the variables discussed previouslyare adjusted.

Finally, by using one or more secondary loops with one or more currentssuch as secondary loop 221 with secondary current 222, and secondaryloop 211 with secondary current 212; the operating volume can beappropriately shaped and extended. For example, as was explainedpreviously, the magnetic field due to the primary loop 103 tends to bestronger in the center. In conjunction with suppressing the magneticfield in the center as discussed above and shown in FIG. 3, one or moreloops similar to secondary loop 221 carrying secondary currents ofvarying amplitude and phase difference can be used to shape theoperating volume by, for example, changing the symmetry or extending theoperating volume. These loops may also be differently shaped dependingon the requirements for the operating volume.

It would be obvious to one having skill in the art that whilerectangular loops are demonstrated above, the techniques outlined herecan be extended to non-rectangular shapes, including, for example,circles, ellipses or other shapes.

While at the design phase a designer has control of all of thevariables, once the NFC antenna is built and used within an operatingmobile device, only some of the variables can be adjusted within thesecondary loops, such as the amplitudes and phase differences of thesecondary currents. So, for example, as the mobile device operatingcharacteristics change over time, this may require that the amplitudesand phase differences also be altered so as to ensure that the NFCantenna continues to operate within the performance requirements.

Furthermore, it is likely that different mobile devices will havedifferent designs and therefore modify the magnetic field produced bythe primary loop in the NFC antenna in different ways. Thus theadjustments required for different mobile devices may differ from oneanother. It would be cost-inefficient, given the requirements of atypical supply chain for a mobile device manufacturer, to find ancombination by optimizing all of the variables for each mobile device.

To meet these further challenges, in one embodiment, the physicalconfiguration of the primary and secondary loops, that is, the shape,dimensions, number of secondary loops, and placement of the secondaryloops is kept the same for each mobile device. However, the amplitudesand phase differences of the secondary currents are adjusted for eachdifferent device so as to ensure that the NFC antenna operates withinthe performance requirements of the standards. For example, withreference to FIG. 4, secondary loop currents 212 and 222 are adjusted soas to meet the requirements of NFC antenna 100.

In another embodiment, for a given mobile device, the amplitudes andphase differences are dynamically adjusted over time so as to ensurethat the NFC antenna continues to operate within the performancerequirements. This allows for compensation as the operatingcharacteristics of the mobile device change over time.

In one embodiment, this adjustment of the amplitudes and phasedifferences of the secondary currents are performed using varioustechniques. In one embodiment, the adjustment is based on measurementsof the magnetic field distribution. For example, based on resultsobtained using known measurement solutions such as those provided byvendors such as Keysight®, the amplitudes and phase differences ofsecondary currents such as currents 212 and 222 are adjusted to ensureconformance with performance requirements. In another embodiment,adjustment is based on computer simulations. In a further embodiment,adjustment is based on a combination of simulation and measurement.

Various algorithms are used to adjust the secondary currents as well. Inone embodiment, this involves using techniques such as learningalgorithms, artificial neural networks, evolutionary algorithms, andtuning algorithms. In a further embodiment, historical data is used toperform the adjustment. In yet another embodiment, adjustment and tuningis performed using an “offline-online” dual stage method. In the on-linestage, measurements are continually captured in real-time whileadjustments are made to ensure conformance. In the offline stage, thiscaptured measurement data is processed and used as inputs to, forexample, machine learning algorithms to refine the adjustments to beused in the online stage. Therefore, over a period of time, it is likelythat the adjustment process becomes more efficient.

In a further embodiment, the adjustments are performed using anadjustment module such as adjustment module 501 as shown in FIG. 5. InFIG. 5, adjustment module 501 controls the secondary currents 212 and222, while reading primary current 102. Then the adjustment module 501performs adjustments to secondary currents 212 and 222 using varioustechniques as outlined above. In a further embodiment, the adjustmentmodule is implemented in software. In another embodiment, the adjustmentmodule is implemented in hardware. In yet another embodiment, theadjustment module is implemented both in hardware and software. In theembodiments where the adjustment module is implemented in software, inone embodiment, the adjustments are performed using an applicationrunning on the mobile device containing the NFC antenna.

Although the algorithms described above have been described separately,it should be understood that any two or more of the algorithms disclosedherein can be combined in any combination. Any of the methods,algorithms, implementations, or procedures described herein can includemachine-readable instructions for execution by: (a) a processor, (b) acontroller, and/or (c) any other suitable processing device. Anyalgorithm, software, or method disclosed herein can be embodied insoftware stored on a non-transitory tangible medium such as, forexample, a flash memory, a CD-ROM, a floppy disk, a hard drive, adigital versatile disk (DVD), or other memory devices, but persons ofordinary skill in the art will readily appreciate that the entirealgorithm and/or parts thereof could alternatively be executed by adevice other than a controller and/or embodied in firmware or dedicatedhardware in a well known manner (e.g., it may be implemented by anapplication specific integrated circuit (ASIC), a programmable logicdevice (PLD), a field programmable logic device (FPLD), discrete logic,etc.). Also, some or all of the machine-readable instructions depictedherein can be implemented manually as opposed to automatically by acontroller, processor, or similar computing device or machine. Further,although specific algorithms are described, persons of ordinary skill inthe art will readily appreciate that many other methods of implementingthe example machine readable instructions may alternatively be used. Forexample, the order of execution of the blocks may be changed, and/orsome of the blocks described may be changed, eliminated, or combined.

It should be noted that the algorithms illustrated and discussed hereinas having various modules which perform particular functions andinteract with one another. It should be understood that these modulesare merely segregated based on their function for the sake ofdescription and represent computer hardware and/or executable softwarecode which is stored on a computer-readable medium for execution onappropriate computing hardware. The various functions of the differentmodules and units can be combined or segregated as hardware and/orsoftware stored on a non-transitory computer-readable medium as above asmodules in any manner, and can be used separately or in combination.

While particular implementations and applications of the presentdisclosure have been illustrated and described, it is to be understoodthat the present disclosure is not limited to the precise constructionand compositions disclosed herein and that various modifications,changes, and variations can be apparent from the foregoing descriptionswithout departing from the spirit and scope of an invention as definedin the appended claims.

It should be understood that the drawings and detailed descriptionherein are to be regarded in an illustrative rather than a restrictivemanner, and are not intended to be limiting to the particular forms andexamples disclosed. On the contrary, included are any furthermodifications, changes, rearrangements, substitutions, alternatives,design choices, and embodiments apparent to those of ordinary skill inthe art, without departing from the spirit and scope hereof, as definedby the following claims. Thus, it is intended that the following claimsbe interpreted to embrace all such further modifications, changes,rearrangements, substitutions, alternatives, design choices, andembodiments.

1. A system for an antenna for near field communications (NFC), saidantenna comprising: a primary loop with a primary current to produce amagnetic field; one or more secondary loops with one or more secondarycurrents; wherein by adjusting one or more variables associated withsaid one or more secondary loops, said magnetic field is modified toensure antenna operation within a defined operating range; and said oneor more variables comprising (1) a number of secondary loops, (2) one ormore amplitudes of the one or more secondary currents in the one or moresecondary loops, (3) one or more phase differences between the one ormore secondary currents in the one or more secondary loops and theprimary current in the primary loop, (4) one or more shapes of the oneor more secondary loops, (5) one or more dimensions of the one or moresecondary loops, and (6) one or more placements of the one or moresecondary loops.
 2. The system of claim 1, wherein said magnetic fieldis either enhanced or suppressed by adjusting at least one placement ofat least one of the one or more secondary loops, and at least one phasedifference of at least one of the one or more secondary currents.
 3. Thesystem of claim 1, further wherein by adjusting said one or morevariables associated with said one or more secondary loops, saidmagnetic field is modified to ensure antenna operation within a definedoperating range within an operating volume.
 4. The system of claim 1,further wherein by adjusting said one or more variables associated withsaid one or more secondary loops, said operating volume is modified. 5.The system of claim 1, wherein said magnetic field is either enhanced orsuppressed by adjusting at least one amplitude of at least one of theone or more secondary currents; and at least one phase difference of atleast one of the one or more secondary currents.
 6. The system of claim5, wherein said adjustment is performed using an adjustment module. 7.The system of claim 1, wherein said adjusting is performed based on atleast one of: numerical simulation; analytical techniques; and testing.8. The system of claim 1, wherein said adjusting is performed to modifysaid symmetry of said magnetic field.
 9. The system of claim 1, whereinsaid primary loop is rectangular.
 10. The system of claim 1, whereinsaid one or more secondary loops are rectangular.
 11. A method for anantenna for near field communications (NFC), said antenna comprising: aprimary loop with a primary current to produce a magnetic field; one ormore secondary loops with one or more secondary currents; wherein saidmethod comprises: modifying said magnetic field to ensure antennaoperation within a defined operating range; said modifying based onadjusting one or more variables associated with said one or moresecondary loops, wherein said one or more variables comprise (1) anumber of secondary loops, (2) one or more amplitudes of the one or moresecondary currents in the one or more secondary loops, (3) one or morephase differences between the one or more secondary currents in the oneor more secondary loops and the primary current in the primary loop, (4)one or more shapes of the one or more secondary loops, (5) one or moredimensions of the one or more secondary loops, and (6) one or moreplacements of the one or more secondary loops.
 12. The method of claim11, wherein said modifying comprises either enhancing or suppressingsaid magnetic field by adjusting at least one placement of at least oneof the one or more secondary loops, and at least one phase difference ofat least one of the one or more secondary currents.
 13. The method ofclaim 11, further wherein by adjusting said one or more variablesassociated with said one or more secondary loops, said magnetic field ismodified to ensure antenna operation within said defined operating rangewithin an operating volume.
 14. The method of claim 11, further whereinsaid modifying comprises shaping said operating volume.
 15. The methodof claim 11, wherein said modifying of said magnetic field compriseseither enhancing or suppressing said magnetic field by adjusting atleast one amplitude of at least one of the one or more secondarycurrents, and at least one phase difference of at least one of the oneor more secondary currents.
 16. The method of claim 15, wherein saidadjustment is performed using an adjustment module.
 17. The method ofclaim 11, wherein said adjusting is performed based on at least one of:numerical simulation; analytical techniques; and testing.
 18. The methodof claim 11, wherein said modifying comprises performing said adjustingto modify said symmetry of said magnetic field.
 19. The method of claim11, wherein said primary loop is rectangular.
 20. The method of claim11, wherein said one or more secondary loops are rectangular.